Add a notebook on how IndShockConsumerType is solved.

[pkofod]

@mgerring would love your input on this. This comes from a person who's read the code and written down the steps, but you may have some important/interesting things to add.

The title says "how" but it's not a math notebook, it's a notebook on how the actual program is organized.

[pkofod]

Oops, tagged the wrong matt @mnwhite

[mnwhite]

In addition to Karsten looking at this (it was written somewhat with him in mind), I've shared this with my colleague Jorge Soares.

[llorracc]

This needs to be merged with the one that Karsten made.

[pkofod]

Is that this one? https://github.com/econ-ark/DemARK/blob/b009a0922a540559274e4e5718de27a5b3d8c6fb/notebooks/Quickstart_tutorial/Quick_start_with_solution.ipynb

[llorracc]

@sbenthall is working on a "how to get started with HARK" project that this is part of

[sbenthall]

My next steps:

1. Review the notebook in this PR, merge if good
2. Look at the Quickstart notebook and see if this can be combined with it
3. Move both of these into HARK/examples/ after Move non-reusable model code to examples/ HARK#442 is merged as part of DemARK build recipes HARK#459

[sbenthall]

Notebook looks very good to me. Next steps now in issue #81 . Merging.